1.0 Field of the Invention
This invention relates generally to conventional wet vacuum cleaners consisting of a tub-like lower part and--sealingly mounted thereon--an upper part with an integrated suction blower for generating a reduced pressure in a stock liquor tank and more particularly to such a cleaner in which the lower part or a portion of the stock liquor tank includes a suction line leading from the stock liquor tank into a powder container.
2.0 Discussion of Related Art
It is known that a stock liquor tank containing a detergent solution can be provided for supplying institutional washing or dishwashing machines with the detergent solution. The detergent solution is pumped as required from the stock liquor tank into the washing or dishwashing machines. To prepare the stock liquor from a powder or powder-form detergent, a metering unit is associated with the stock liquor tank. The powder is poured into the metering unit from a powder container or the powder container as a whole is introduced into the metering unit and slit open. Powder-form detergent is delivered in batches from the metering unit into a dispensing trough in which it mixes with inflowing water to form the stock liquor forming the detergent solution for the washing or dishwashing machine. The stock liquor is then directly introduced into the stock liquor tank. The detergent solution is removed from the stock liquor tank in accordance with the requirements of the particular washing or dishwashing process.
Filling the metering unit with the powder-form detergent is not without problems. It is frequently accompanied by dust emission which is unpleasant and a health hazard to the machine operator, particularly in the case of the strongly alkaline detergent powders typically used for dishwashing. Unwanted dust emission can occur both during the introduction of powder containers into the metering unit and during the pouring or scooping of powder from the container into the metering unit.
The holding capacity of known metering units for supplying known stock liquor tanks with powder-form detergent is typically 5 kg so that only 5 kg powder containers can be accommodated in the metering units. In addition, the powder is normally removed from the metering units and the powder/water mixture delivered to the stock liquor tank under the effect of gravity. Accordingly, the metering units are normally arranged above a stock liquor tank. This prevents the holding capacity of the metering units from being increased as required unless holders of complicated construction are provided for the metering unit.
Conventional stock liquor tanks are in the form of tanks per se or canisters and comprise a feed line for the stock liquor prepared by means of a metering unit and an outlet line for delivering the stock liquor from the stock liquor tank to institutional dishwashing or washing machines.
3.0 Summary of the Invention
The problem addressed by the present invention is to enable a stock liquor to be directly prepared from the powder container holding powder-form detergent without any dust emission and to keep the stock liquor ready for supplying institutional dishwashing or washing machines.
In an apparatus of the type mentioned previously, the solution provided by the invention is characterized in that the opening of the suction line on the inside of the stock liquor tank is arranged at a distance from the point where the suction line enters the lower part, in that a fresh water line opens into the stock liquor tank, its water outlet opening being directed onto a stream of powder to be drawn through the suction line, and in that the stock liquor tank comprises another stock liquor line operatively connected to a pump and leading out from the stock liquor tank with a stock liquor inlet in the base of the tank for pumping off the stock liquor from the lower part.
With the arrangement according to the invention, powder-form detergent can be directly transported from the powder container, which is also the retail container, into the stock liquor tank without any emission of dust. In the stock liquor tank, water from a fresh water line is added to the stream of powder drawn through the suction line to prepare the stock liquor forming the detergent solution for institutional dishwashing or washing machines. Accordingly, the preparation of a stock liquor from powder-form detergent and the supply of institutional dishwashing or washing machines with this stock liquor is as simple and safe in its handling as the dispensing of liquid detergent. There is no longer any need for powder-form detergent to be transferred from the powder container to a metering unit, for example by pouring or by scooping.
Compared with known metering units, the quantity of powder which can be accommodated in the metering unit is considerably increased. Instead of the usual 5 kg of powder, powder can now be directly removed from large powder containers, for example 25 kg or even 200 kg bags. This affords the further advantage that the arrangement according to the invention--as a central unit in the form of a powder dispenser--has the capacity to supply several dishwashing or washing machines.
The stock liquor can be directly pumped from the stock liquor tank through the stock liquor line. The stock liquor line operatively connected to a pump is provided for this purpose.
To ensure that the powder drawn into the stock liquor tank through the suction line and issuing from the suction line is not deposited on the inside wall of the lower part of the tank when the jet of water from the fresh water line impinges on the powder, the opening of the suction line on the inside of the stock liquor tank is arranged at a distance from the point where the suction line enters the lower part.
In another embodiment of the invention, the opening of the suction line on the inside of the stock liquor tank is positioned below the point where the suction line enters the lower part, and the opening of the fresh water line on the inside of the stock liquor tank is likewise positioned below the point of entry of the suction line and/or outside the suction line. Accordingly, when the fresh water continues flowing, particularly after the suction blower has been switched off, water is prevented from entering the suction line and flowing into the powder container, for example through the suction line. The fresh water is prevented from flowing back against gravity by the difference in level between the point of entry and the opening of the suction and/or the separation of the water and powder inlets.
In another particularly advantageous embodiment of the invention, the suction line comprises an elbow or bend directed downwards to the bottom of the stock liquor tank in an extension on the inside thereof.
Another embodiment of the invention which ensures that the powder and fresh water are thoroughly mixed in characterized in that, in an extension on the inside of the stock liquor tank with an outlet opening directed towards the bottom thereof, the fresh water line opens into a bend and, after the bend, the suction line continues to a point situated close to the inner wall of the lower part. This is another measure which prevents the fresh water introduced into the suction line from flowing back. In addition, the fact that, after the bend, the suction line continues to a point situated near the inner wall of the lower part ensures that the powder/water mixture impinges on the inner wall at that point so that the powder particles are mechanically stressed and disintegrate, thus accelerating their dissolution in the prepared stock liquor.
Another embodiment of the invention is characterized in that, in its extension on the inside of the stock liquor tank with the bend, the suction line terminates in the longitudinal axis of the lower part with its opening directed towards the bottom of the tank and, in its extension on the inside of the stock liquor tank, the fresh water line is formed above the opening by a ring line concentrically surrounding the opening and delivering a jet of water directed onto the stream of powder issuing from the suction line from preferably four nozzles inclined at an angle of preferably 45.degree. for a flat-jet opening angle of preferably 65.degree.. In this embodiment, too, the powder issuing from the suction line can readily be made up into the stock liquor.
To ensure that overly large undissolved powder particles do not enter the stock liquor line, another embodiment of the invention is characterized in that a filter plate is arranged in the lower part below the opening of the suction line on the inside of the stock liquor tank.
Another embodiment of the invention is characterized in that, for pumping off the stock liquor from the stock liquor tank, an immersion pump with an intake opening below the filter plate towards the bottom of the tank, and a delivery opening communicating with the second stock liquor line on the pressure side is arranged in the lower part. In this way, a pump for supplying institutional dishwashing or washing machines with stock liquor prepared in the stock liquor tank can readily be integrated in the stock liquor tank in a space-saving arrangement.
To whirl or stir up powder particles which have settled on the filter plate but have not yet dissolved, another embodiment of the invention is characterized in that the stock liquor line has branches in the lower part of which the openings are directed onto the top of the filter plate.
In another embodiment of the invention, at least one pump, preferably in the form of a diaphragm pump or flow-inducing pump, is arranged in the stock liquor line outside the stock liquor tank.
In another embodiment of the invention, two pumps are included for pumping off stock liquor from the stock liquor tank. One pump is the immersion pump with an intake opening below the filter plate towards the bottom of the tank, and a delivering opening communicating with the second stock liquor line on the pressure side is arranged in the lower part of the tank. The immersion pump may in one mode also be used to provide for circulation of the stock liquor within the tank. A second pump, preferably in the form of a diaphragm pump or flow-inducing pump, is arranged in the stock liquor line outside the stock liquor tank, for also pumping stock liquor from the tank.
Another embodiment of the invention is characterized in that, instead of or in addition to the branches of the stock liquor line, a propeller stirrer or stirring rod is rotatably mounted above the filter plate in the stock liquor tank to whirl or stir up any powder particles which have settled on the filter plate.
In another embodiment of the invention, the base of the lower part comprises an outlet with a stock liquor line connected thereto. This is particularly useful when a membrane pump or flow inducing pump is arranged in the stock liquor line for the measured delivery of stock liquor to institutional dishwashing or washing machines.
To supply several institutional dishwashing or washing machines with stock liquor from the arrangement according to the invention, the invention is further characterized in that the stock liquor line comprises branches outside the stock liquor tank for supplying several dishwashing or washing machines.
To prevent the liquid levels inside the stock liquor tank from rising to such an extent that stock liquor can enter the suction line, or falling to such an extent that the intake opening of the immersion pump is left dry or the stock liquor line runs dry into the vicinity of a pump arranged therein, another embodiment of the invention is characterized in that two level control electrodes are arranged on the inner wall of the lower part.
In another embodiment of the invention, the stock liquor tank can be made mobile by mounting on a frame comprising wheels and a handle in the form of a handcart or trolley.
To complete the mobile unit, another embodiment of the invention is characterized in that a mains coupling unit and electrical switches are arranged on the roller-mounted frame.
Another embodiment of the invention is characterized in that at least one pump is mounted on the frame where it is arranged in the stock liquor line outside the stock liquor tank.
Another advantageous embodiment of the invention is characterized in that, to make it easier to handle, the suction line is flexible and, more particularly, is in the form of a hose.
To ensure that powder is drawn uniformly and continuously into the suction line from a powder container, another embodiment of the invention is characterized in that, on its side remote from the stock liquor tank, the suction line terminates in a suction pipe which dips into the powder container and which is surrounded by a tubular jacket with an annular gap in between, the suction pipe and the tubular jacket together forming a suction lance terminating in an annular nozzle on the suction opening side.
To create a turbulence compartment before the end of the suction lance on the inside of the tank, another advantageous embodiment of the invention is characterized in that, on the suction opening side, the suction lance has a cage-like protective basket projecting beyond the end of the suction pipe.
Finally, another embodiment of the invention is characterized in that, on its inside, the suction pipe is provided at its lower end with a flow resistance element. This enables the quantity of powder taken in to be controlled.